卷扬机-井字架-吊篮提升系统相当普遍地被应用在建筑施工中,由于没有什么有效的安全保护装置,时有伤亡事故发生。所以,施工的安全性也一直是人们普遍关心的问题。目前现场施工安全规范要求在井字架顶端以下2.5m处装一行程开关(图1),当吊篮行至这个地方时,吊篮撞动行程开关,卷扬机自动断电,抱闸停车,来防止吊篮被拉顶到井字架端部。但这种方法只有在整个系统安装固定后,再爬上并字架安装开关和架设控制线,既增加了现场的混乱又麻烦,操作人员也不直观,如果需要重新改变限定位置,就显得很困难,且开关使用多是一次性的,也不经济。我们经过反复研究设 The hoisting machine - derrick frame - basket lifting system is quite commonly used in building construction. Because there is no effective safety protection device, casualties occur. Therefore, the safety of construction has always been a common concern. At present, the on-site construction safety specification requires a position switch 2.5 meters below the top of the derrick (Fig. 1). When the basket reaches this point, the cradle hits the limit switch, the hoist automatically shuts off, and the holding brake stops. Prevent the basket from being pulled up to the end of the derrick. However, this method only adds to the installation and fixing of the entire system, and then climbs and installs the switch and erects the control line, which not only increases the confusion and trouble of the site, but also makes the operator inconvenient. If it is necessary to change the limited position again, it becomes very obvious. Difficulties, and the use of switches is mostly disposable and not economical. After repeated studies, we